In the drilling of boreholes into the earth for certain constructions such as architectural structures and support pilings, it is desirable and often critical that large boreholes be placed in the earth at numerous critical locations within very small tolerances for error, both in the location of the borehole centerline and in the vertical alignment of the borehole centerline.
For example, in the construction of the Alaskan pipeline, much of the actual pipeline will be located above the tundra, supported from vertical pilings which have been sunk through the tundra. The specifications for placing these pilings call for the maximum borehole depth of 50 feet with an error in placing the borehole at the correct surveyed point of less than three inches, and a vertical alignment error of less than three inches in a 50 foot length. Thus, it can be seen that normal boring rigs are incapable of placing such boreholes with such accuracy because of their lack of such sensitive alignment systems.
This invention provides systems and methods for placing the boring rig directly over the survey point in direct vertical alignment thereabove.